Lasers using a gas as the radiation-emitting medium can generate pulsed beams of very short wavelengths, ranging from the near to the far ultraviolet, upon stimulation of the gas by high-intensity electrical discharges of very short duration. With nitrogen, carbon dioxide or hydrogen as the emitting gas, for example, wavelengths of 3370, 1930, 1600 and 1200 A can be generated.
The gas present in an elongate cavity can be stimulated with either of two modes of electrical excitation, i.e. longitudinally with the aid of a pair of electrodes at opposite ends of the cavity or transversely by means of two electrodes paralleling the optical cavity axis. Transverse excitation is known to be more efficient and is therefore usually preferred.
Conventional systems for causing such transverse excitation utilize conductor strips sometimes referred to as Blumlein lines. Such strip lines, generally consisting of metal foils separated by insulating material of low dielectric constant (e.g. Mylar), serve to convey the electrical excitation pulses in properly phased relationship to the electrodes flanking the cavity; they may be given, for this purpose, a variety of configurations with rectangular, triangular, segmental or paraboloidal outline, for example. In all these instances, however, the coupling between the source of excitation pulses and the laser cavity creates problems, especially with UV radiation which requires a low impedance of the discharge circuit and steep pulse flanks compatible with the short transition periods of such high-frequency lasers. The solutions heretofore adopted call for the storage of large amounts of electrical energy with the aid of sizable capacitors, resulting in a bulky structure which is only limitedly manipulable and creates difficulties of electrical insulation and of shielding against the emission of objectionable noise signals. Even with discharge lines formed from a series of capacitors with ceramic bodies having a high dielectric constant, as already proposed for improving the efficiency of a gas laser, no significant reduction in the overall dimensions of such structures has been realized up to now. Moreover, the piezoelectric properties of ceramic dielectrics convert electric pulses into acoustic shock waves which tend to cause cracks in the bodies of such capacitors.